Houthi fighters in Yemen fired missiles at a military base of the Saudi-backed government in Marib province, northeast of the capital Sanaa, on Tuesday, killing seven people including relatives of the chief of staff, three military sources said.

Yemeni government troops took control Saturday of the city of Ataq, two days after deadly clashes between loyalists and southern separatists in the capital of Shabwa province, a pro-government source said.

Southern separatists seized two Yemeni government military bases near the southern port of Aden early on Tuesday, triggering fresh clashes between nominal allies that have complicated UN peace efforts, residents and officials said.

Yemen's warring parties have failed to pull troops from the main port under a month-old truce, putting the first major diplomatic breakthrough of the four-year war in jeopardy and reviving the threat of an all-out assault that could unleash famine.